:root {
  --bg: #f7f8fa;
  --card: #ffffff;
  --accent: #2b6cb0;
  --text: #222;
  --muted: #666;
  --maxwidth: 1100px;
  --radius: 12px;
}

html, body {
  height: 100%;
}

body {
  margin: 0;
  font-family: "游ゴシック", "Yu Gothic", "Noto Sans JP",
               system-ui, -apple-system, "Hiragino Kaku Gothic ProN", "Meiryo", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.75;
  padding: 24px 16px;
  box-sizing: border-box;
}

/* 全体のレイアウト */
.container {
  max-width: var(--maxwidth);
  margin: 0 auto;
}

.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: 0 6px 20px rgba(20, 30, 40, 0.06);
  padding: 28px;
  overflow: hidden;
}

/* 見出しなど */
.kicker {
  display: inline-block;
  font-weight: 700;
  color: var(--accent);
  font-size: 13px;
  letter-spacing: 0.06em;
  margin-bottom: 8px;
}

h2 {
  margin: 6px 0 14px;
  font-size: 22px;
  line-height: 1.25;
}

.lead {
  font-size: 16px;
  color: var(--muted);
  margin-bottom: 18px;
}

.section-body p {
  margin: 0 0 12px;
}

/* 引用文 */
.quote {
  border-left: 4px solid var(--accent);
  padding: 12px 14px;
  background: linear-gradient(90deg, rgba(43,108,176,0.03), rgba(0,0,0,0));
  margin: 14px 0;
  border-radius: 8px;
  color: var(--text);
  font-weight: 500;
}

/* ご挨拶セクション */
.greeting-section {
  margin-top: 32px;
  padding-top: 24px;
  border-top: 1px solid #e0e4ea;
}

.greeting-head {
  display: flex;
  gap: 14px;
  align-items: center;
  margin-bottom: 10px;
  flex-wrap: wrap;
}

.avatar {
  width: 72px;
  height: 72px;
  border-radius: 50%;
  flex: 0 0 72px;
  object-fit: cover;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.meta {
  font-size: 13px;
  color: var(--muted);
}

/* 学習の十か条 */
.rules {
  margin: 28px 0;
  background: #f9fafc;
  border-left: 4px solid var(--accent);
  border-radius: 12px;
  padding: 22px 26px;
}

.rules-title {
  font-size: 18px;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 12px;
}

.rules-list {
  margin: 0;
  padding-left: 1.4em;
}

.rules-list li {
  margin-bottom: 8px;
  line-height: 1.6;
  list-style: decimal;
}

/* ボタン */
.btn {
  display: inline-block;
  padding: 12px 18px;
  border-radius: 10px;
  text-decoration: none;
  font-weight: 600;
  margin-top: 24px;
  background: var(--accent);
  color: white;
  transition: background 0.3s ease;
}
.btn:hover {
  background: #1a4f8a;
}

/* ✅ スマホ対応（600px以下） */
@media (max-width: 600px) {
  body {
    padding: 16px 12px;
    line-height: 1.8;
  }

  .card {
    padding: 22px 18px;
    box-shadow: none;
    border-radius: 0;
  }

  h2 {
    font-size: 20px;
  }

  .lead {
    font-size: 15px;
  }

  .avatar {
    width: 64px;
    height: 64px;
    margin-bottom: 4px;
  }

  .greeting-section {
    padding-top: 18px;
  }

  .rules {
    padding: 16px 18px;
  }

  .btn {
    width: 100%;
    text-align: center;
    padding: 14px;
    font-size: 16px;
  }
}

/* 印刷用 */
@media print {
  body {
    background: white;
    padding: 0;
  }
  .card {
    box-shadow: none;
  }
}
.back-to-top {
  position: fixed;
  bottom: 30px;        
  right: 30px;      
  background-color:  #00a0a5; 
  color: #ffffff;       
  padding: 12px 20px;   
  border-radius: 50px;  
  text-decoration: none; 
  font-weight: bold;
  box-shadow: 0 4px 6px rgba(0,0,0,0.2);
  transition: all 0.3s ease;
  z-index: 9999;        /* 常に最前面に表示 */
}
.back-to-top:hover {
  background-color:#007b80; /* 少し明るく */
  transform: translateY(-3px);
  box-shadow: 0 6px 10px rgba(0,0,0,0.3);
}